Propagating electromagnetic radiation is composed of two orthogonally polarized components—known as the transverse electric and transverse magnetic fields. In many applications, it is necessary or desired to separately control the transverse electric (TE) or the transverse magnetic (TM) polarization. Device performance which varies based on polarization state may be important in optoelectronics, thereby allowing the possibility of multi-functioning devices. Birefringence is a property of a material to divide electromagnetic radiation into these two components, and may be found in materials which have two different indices of refraction, referred to as n⊥ and n81  (or np and ns), in different directions, often orthogonal, (i.e., light entering certain transparent materials, such as calcite, splits into two beams which travel at different speeds). Birefringence is also known as double refraction. Birefringence may serve to provide the capability of separating these two orthogonal polarization, thereby allowing such devices to manipulate each polarization independently. For example, polarization may be used to provide add/drop capabilities, beamsplit incoming radiation, filter, etc.
However, a need therefore exists for devices in which polarization of traversing and incident electromagnetic spectrum may be controlled over a broad spectral range, thereby providing broadband polarization control.